航空材料学报

Fabrication and Properties of Microarc Oxidation Coatings on Ti₃Al-Based Alloy

LI Xi-jin, CHENG Guo-an, XUE Wen-bin, CHENG Yun-jun

2007, 27(5): 1-6.

[Abstract](1361) [PDF 1669KB](207)

Abstract:
Ceramic coating with a thickness of 120 m was fabricated on a Ti3Al-based alloy by microarc oxidation in silicate electrolyte.The growth rates of the coating were different during processing with different time.The thickness of ceramic coating increased with increasing of treatment time.Both microstructure and microhardness showed a structure with two layers in the coating: the inner layer and the outer layer.The main phase constituent of the coating was(Ti0.6Al0.2Nb0.2)O2.Microhardness of the coating was about 3 times as that of the substrate.Micro-scratch test revealed that there was a excellent adhesion between coating and substrate.The corrosion resistance of the coating was much better than that of the substrate.

Investigation on Microstructures and Properties of NbCr₂ Laves Phase Alloys Prepared by Mechanical Alloying Followed by Hot Pressing

XIAO Xuan, LU Shi-qiang, MA Yan-qing, YAN Jian-wu, HU Ping

2007, 27(5): 7-11.

[Abstract](1625) [PDF 644KB](251)

Abstract:
Laves phase NbCr2 alloys with a stoichiometric composition were prepared by mechanical alloying followed by hot pressing.Microstructures and properties were investigated on Laves phase NbCr2 alloys prepared from 20h mechanically alloyed powders of elemental chromium and niobium powders by hot pressing at 1200℃,1250℃ and 1300℃ for different time.The results indicate that Laves phase NbCr2 alloy with homogeneous microstructure and micro-and/or nano-grains is obtained by hot pressing at 1250℃ for 0.5h,moreover,the alloy has a relative density of 97.1% and a room temperature fracture toughness more than 5.07MPa·m1/2.Compared with Laves phase NbCr2 alloy with a fracture toughness of 1.50MPa·m1/2 prepared by arc-melting,the fracture toughness of Laves phase NbCr2 alloy prepared here increases greatly,the effect of fine grain toughening has been fully realized.

Evolution of Carbides and Their Effects in Single Crystal Superalloy

LIU Li-rong, JIN Tao, SUN Xiaofeng, GUAN Heng-rong, HU Zhuang-qi

2007, 27(5): 12-16.

[Abstract](1579) [PDF 784KB](242)

Abstract:
Transformation mechanism of carbides and their effect on the stress rupture property were investigated in a Ni-base single crystal superalloy with microcontent of carbon.The results are as follows: a little carbon MC carbide forms in interdendritic region in the alloy with 0.015% carbon.During the heat treatment and stress rupture tests,part of MC carbide transforms into M6C carbide.Secondary M6C carbides precipitate from γ matrix during higher temperature stress rupture tests and M23C6 during lower temperature stress rupture tests.Two type of secondary carbide precipitate can be acted as obstacles to block the dislocations motion.Compared with the base alloy,the stress rupture properties of alloy B with 0.015%carbon are improved.

Influences of La-Rich RE on the Microstructure and Mechanical Properties of Mg-10Li-4Al Alloy

LIU Bin, ZHANG Mi-lin, HU Yao-yu, WU Rui-zhi

2007, 27(5): 17-21.

[Abstract](1509) [PDF 681KB](261)

Abstract:
The influence of varied contents misch metal on microstructure of the Mg-10Li-4Al alloys was studied,and the effect of RE-compound in alloys was analyzed as well.In addition,the mechanical properties of alloys at room temperature were measured.The results indicate that the additions of lanthanum misch metal refine the grain and lead to the formation of rod-shaped Al3La compound which restrains the formation of Mg17Al12 and MgLiAl2 phases,consequently,the mechanical properties were improved.With the increasing amount of Al3La compound in alloy and it size become to coarsening,the strength of the alloys improved slowly and the elongation decreased.

Effect of Isothermal Forging on Microstructure of Ti-17 Powder Alloy

ZHAO Zhang-long, GUO Hong-zhen, TANG Hui-ping, LIU Hai-yan, TIAN Yun, YAO Ze-kun

2007, 27(5): 22-25.

[Abstract](1488) [PDF 692KB](215)

Abstract:
Ti-17 powder alloy was prepared by the method of sintering + isothermal forging,and the densities and transformation of microstructure in the process of preparing powder alloy were investigated.The results indicate that the relative densities of-140 mesh sintering bar and-80/+140 mesh sintering bar are 98.06% and 93.55% respectively at the same conditions of sintering,and a number of voids remained in the microstructure of-80/+140 mesh powder sintering bar.The high and low isothermal forging can remove the remaining void effectively after powder alloy sintering,consequently increase the density and get refined and uniform microstructure.Thus the ssintering + isothermal forging is an effective way of preparing high quality powder titanium alloys.

Effect of Heat Treatment on Microstructure and Mechanical Properties of Cast Fe-B-C Alloy

FENG Xi-lan, JIANG Zhi-qiang, FU Han-guang

2007, 27(5): 26-29.

[Abstract](1422) [PDF 668KB](275)

Abstract:
Effect of quenching temperature and cooling rate on the structure and properties of cast Fe-B-C alloy containing more than 1.0%B and lower than 0.2%C has been studied.The results show that the structure of Fe-B-C cast alloy changes from pearlite being prevailing + ferrite + a small amount of martensite to martensite being prevailing + a small amount of pearlite and to martensite matrix,and the hardness increases with the increasing of quenching cooling rate.In the case of water quenching,higher or lower quenching temperature is not advantageous to obtain full martensite.Quenching at 950~1000℃,cast Fe-B-C alloy could obtain the structure of fine lath martensite and boride with high hardness.The hardness and impact toughness of cast Fe-B-C alloy exceed 55HRC and 15J/cm2 respectively.

Superplastic Isothermal Forging Technology of P/M Superalloy

WANG Shu-yun, LI Hui-qu, YANG Hong-tao

2007, 27(5): 30-33.

[Abstract](1693) [PDF 1209KB](845)

Abstract:
The superplastic behavior and isothermal forging technology of FGH96 alloy were investigated in this paper.The experimental results show that grain-refining treated FGH96 alloy obtained extremely significant superplasticity at temperature 1020～1100℃.When as-HIP and HIP+HIF FGH96 alloy was isothermal compressed at the same deformation condition,the flow stress of HIP+HIF FGH96 alloy was significantly reduced.The results of investigation on superplastic isothermal forging process of FGH96 alloy have made it possible to produce large disc forgings with relatively smaller equipment.

Preparation and Characterization of High Nb Containing TiAl Alloying Powder

WANG Yan-hang, ZHAO Li-ming, LIN Jun-pin, WANG Yan-li, QU Xuan-hui, CHEN Guo-liang

2007, 27(5): 34-39.

[Abstract](1520) [PDF 1867KB](360)

Abstract:
Ti-45Al-8.5Nb-0.2W-0.2B-0.02Y(at%) ingot with industrial scale was fabricated using plasma arc furnace and was subsequently machined.High Nb containing TiAl alloying powder was obtained by Ar gas atomization process and its characterization was investigated.It was found that there are three microsegregations in the high Nb containing TiAl alloy composed of fully lamellar microstructure,i.e.β phase,borides and Y2O3.The granularity of high Nb containing TiAl alloying powder is mostly 100~200μm;Oxygen content becomes higher gradually with decreasing powder granularity;Nitrogen content is basically constant;and little carbon exists.The phases of the alloying powder are related with its granularity.The exterior and interior micro-structures of the alloying powder are dendritic.There are four microsegregations in the powder,and they become finer with decreasing powder granularity.

Hot Workability of Ti-6Al-4V Alloy Based on Processing Map

ZHANG Xiao-lu, LI Fu-guo, PENG Fu-hua, HUANG Yong-sheng, SHUAI Chao-lin

2007, 27(5): 40-44.

[Abstract](1485) [PDF 1972KB](252)

Abstract:
Hot workability of Ti-6Al-4V has been investigated by means of hot compression tests carried out in the range of between 750～1050℃ and 0.001～100s-1.A constitutive equation of TC4 alloy for the flow stress has been given.Considered the effects of the deformation temperatures and the stain rates for microstructures of Ti-6Al-4V,processing maps were generated using the dynamic material model(DMM).Unstable deformation regions were defined by Malas' stability criteria.The optimal process parameter of Ti-6Al-4V is at about 800℃ for the deformation temperature and 0.001s-1 for the deformation rate in the processing map.

Process of Fe-Ni-Cu-C Alloy Coarse Powder by Injection Molding

QIAO Bin, SHANG Feng, LI Hua-qiang

2007, 27(5): 45-48.

[Abstract](1474) [PDF 606KB](245)

Abstract:
Fe-Ni-Cu-C mixed powder by injection molding using coarser powder with particle size of 60um was studied.The effect of injection parameters to the quality of green was studied by orthogonal arrays design and statistical analysis method according to the density and strength of the green part.The right debinding and sintering processes were obtained.Results indicated that the sintered part is provided with the best mechanical property when the proportion of H2 and N2 is 1:3 and the sintering temperature is 1225℃,at which,the tensile strength is 360MPa,yield strength is 171MPa and hardness is 54HRB.

Microstructures and Property of SiC/SiC Joints Brazed with Pd-Co-Ni-V Brazing Foils

CHEN Bo, XIONG Hua-ping, MAO Wei, GUO Wan-lin, CHENG Yao-yong, LI Xiao-hong

2007, 27(5): 49-52.

[Abstract](1519) [PDF 1154KB](180)

Abstract:
Wettability of PdCo and PdCo-Valloys on SiC was studied with the sessile drop method.The recently-developed PdCo-(4~20)V-4Ni-Si-B brazing foils were used for SiC joining,and the room-temperature three-point bend strengths of the SiC/SiC joints brazed at 1463 K and 1493 K for 10 min are 52.0 MPa and 6.8 MPa respectively.The micro-analysis results show that there exist the mixture of Pd2Si and CoSi(or Co2Si)+graphite at the interface close to the joined SiC in the joint,while the element V is rich only in the central part of the joint,that is,the phases of V2C are scattered there.

Dry Sliding Wear Behavior of SiC Particulate Reinforced Aluminum Matrix Composites Fabricated Using Pressureless Infiltration Process

LüYi-zhong, WANG Bao-shun, CUI Yan, ZHAO Hui-you, QU Jing-xin

2007, 27(5): 53-57.

[Abstract](1426) [PDF 638KB](224)

Abstract:
The Aluminum matrix composites reinforced with SiC particulates of different sizes and volume fraction were fabricated by pressureless infiltration process.The effect of the size(110μm,63μm,45μm) and volume fraction(15%,25%,35%,45%,55%)of SiC particulate on the friction and wear behaviour of the composites sliding against cemented carbide(80%WC+20%Co)was investigated under dry condition.The wear tests were carried out using a block-on-ring tester at two loads of 196N and 392N under a constant sliding speed of 200rad/min.Worn surface and wear debris were examined by scanning electron microscope(SEM) and energy dispersive spectrometer(EDS).The wear mechanisms were determined.It was showed that the wear resistance of the composites was superior to that of aluminum matrix alloy when the SiC particulate volume fraction was in the range of 15%~35%.The results of the investigation also indicated that the wear rate of the composites decreased with increasing the particulate size and decreasing load.The optimal volume fraction of SiC particulate is at 25%.When the SiC particulate volume fraction was less than 25%,the wear rate of the composites significantly decreased with increasing SiC volume fraction,the wear mechanism of the composites in this period is abrasive wear.When the SiC particulate volume fraction was more than 25%,wear rate of the composites increased with increasing the SiC particulate volume fraction,the composite is characterized by delamination wear and abrasive wear.

Influence of Heat-Treatment and Slurry on Strength and Distribution of Nextel 720 Fiber

HAN Gui-fang, ZHANG Li-tong, CHENG Lai-fei

2007, 27(5): 58-61.

[Abstract](1486) [PDF 1048KB](232)

Abstract:
With two parameter Weibull distribution,the strength distribution of Nextel 720 fiber was investigated.And the fitness of the strength distribution was also conducted by the Kolmogorov test.With slurry infiltration,including silica sol,silica slurry and silicon nitride slurry,the influence of different slurry on the strength and distribution of Nextel 720 fiber were studied.Meanwhile,the influence of heat treatment was also performed.The results show that two parameter Weibull distributions can be used to present the strength distribution of Nextel 720 fiber.It also suggesting that the strength of the fiber decrease sharply after heat treated,and decentrality of the strength is increased.Infiltrated with slurry and heat-treated at the temperature of 800℃,the strength of the fiber are much higher,and the Weibull modulus of the fibers are bigger than that of the as-received fiber tows.While treated at the temperature of 1000℃,the strength of the fiber tows are much lower due to the damage at higher treatment temperature.But the strength are still higher than that of the fiber tows' treated at same temperature without slurry,and the decentrality are also decreased.

Preparation and Characterization of Poly(3,4-ethylenedioxythiophene)/Carbon Nanotube Nanocomposites

HA En-hua, HUANG Da-qing, HA En-ping, WANG Zhi-yong, DING He-yan

2007, 27(5): 62-65.

[Abstract](1402) [PDF 520KB](317)

Abstract:
The preparation of transparent conductive coating with excellent transparence and conductivity was necessary to self-assemble carbon nanotubes into an integrated conductive network effectively in resin media.The combination of carbon nanotubes with polymers offers an attractive route to introduce new electronic properties based on morphological modification or electronic interaction between the two components.Poly(3,4-ethylenedioxythiophene)(PEDOT)/carbon nanotube composites were prepared by in situ potentiostatic deposition of PEDOT onto carbon nanotubes and characterized with TEM、FTIR and Standard four-probe method.TEM studies on the composites showed that a layer of conducting poly(3,4-ethylenedioxythiophene) capsulates the carbon nanotube.The use of standard four-probe method supports results in carbon nanotube,PEDOT and PEDOT/carbon nanotube composites with 10.4S/cm,14.3S/cm and 100S/cm.The synthesis of the nanocomposites with microscopic structure not only forges a solid basis for both the self-assembling of all kinds of nanocomposites for versatile application.

Preparation and Characterization of PMR-type Polyimide Resins Terminated with Phenylethynyl Group

CHEN Jian-sheng, ZUO Hong-jun, GAO Qun-feng, HE Guan-jun, FAN Lin, YANG Shi-yong

2007, 27(5): 66-70.

[Abstract](1615) [PDF 1823KB](372)

Abstract:
The PMR-type polyimide resin PEPA-15 with calculated molecular weight of 1500 was prepared using 2,3,3',4'-biphenyltetracarboxcylic anhydride(a-BPDA),4-phenylethynyl aniline(p-PDA),and 4-phenylethynylphthalic anhydride(4-PEPA).The PEPA-15 monomer solution has good stability at room temperature,and the melt processability of PEPA-15 molding powders and prepregs were characterized using AR-2000 rheometer.The polyimide resin cured at 371℃ showed excellent thermal stability,and after postcure at high temperature for 2 hours,the T300 carbon fiber reinforced PEPA-15 composite exhibited no change of storage modulus before 450℃ in Dynamic Mechanical Analysis(DMA) test.

Fabrication of Al₃Ti/Al Composites by Reaction Synthesis Based on SHS

HUO Xiao-wei, WANG Shu-qi, CHEN Kang-min

2007, 27(5): 71-76.

[Abstract](1526) [PDF 1832KB](292)

Abstract:
Al3Ti/Al composites were in situ fabricated by preheating Al and Ti powders mixture at certain temperatures.The fabrication mechanism of Al3Ti was studied by thermodynamics analysis and the influence factors were also discussed.Results indicate that: the melting of Al induces the reaction between Al and Ti powders.When Al and Ti mixture preforms is preheated at the higher temperature than the start temperature of thermal explosion reaction,coarse particulate of Al3Ti is made by thermal explosion mechanism.When the preheated temperature is lower than the start temperature of thermal explosion reaction,the reaction mechanism is diffusion and thermal explosion.The morphology of the Al3Ti/Al composites is influenced by the preheated temperature,the granularity of Ti particles and the cooling velocity.By making use of some cooling technique,Al3Ti/Al composites with excellent capability were prepared when preheated at 665℃.The hardness of the Al3Ti/Al composites is 3.6 times of pure Al and the wear capability is high.

Study on Sizing Modification of Basalt Fibers

CAO Hai-lin, ZHANG Chun-hong, ZHANG Zhi-qian, GAO Yuan

2007, 27(5): 77-82.

[Abstract](1474) [PDF 1740KB](290)

Abstract:
The organic/inorganic hybrid sizing was synthesized by sol-gel method.The IR and AFM analysis results indicated that the epoxy/SiO2 nano-hybrid material was synthesized.The basalt fibers were surface modified by organic/inorganic nano-hybrid sizing.The surface morphology of basalt fibers,the multifilament yarn tensile strength and the ILSS of its composites were investigated.The results indicated that when the basalt fibers were modified by hybrid sizing with optimum concentration the surface morphology of the fiber was rougher and the tensile strength was increased,meanwhile the ILSS of its composites was improved.All of these research proved that the sizing modification using organic/inorganic nano-hybrid sizing was an effective method for improving basalt fiber and its composites properties.

Prediction of the Effective Permittivity and Permeability of Magnetically Material Fiber with Resin

GAO Zheng-ping, BI Zhao-yi, WANG Xiao-hong

2007, 27(5): 83-90.

[Abstract](1580) [PDF 950KB](351)

Abstract:
The method for predicting the effective permittivity and effective permeability of the composite of magnetic metal fiber with resin is presented.firstly,The apparent permittivity and apparent permeability of the electric dipole and magnetic dipole of a single fiber was derived.The relation of these apparent parameters with the geometry of the fiber is analyzed;the mechanism of high μ of the fiber is demonstrated.Then,use the Maxwell-Garnett Mode to calculate the effective EM parameters of the composite of the fiber mixed with resin with different distribution are computed.

Effect of Outer Chamfer on Stress Distribution in Single Lap Joint

YOU Min, YAN Zhan-mou, ZHENG Xiao-ling, YU Hai-zhou

2007, 27(5): 91-94.

[Abstract](1477) [PDF 1057KB](264)

Abstract:
The effect of outer chamfering angle near unload ends of adherend and adhesive with different elastic modulus on the stress distribution of adhesively bonded aluminium alloy single lap joint has been investigated using elasto-plastic finite dlement method.The results show that the peak stresses of mid-bondline decrease when adherend is chamfered on the outside,consequently the strength of joint increases,and the peak stresses of mid-bondline decrease gradually as the chamfer angle decreasing.All peak stresses of chamfering joint with high elastic modulus of adhesive,while the influence of chamfer on the peak stresses of mid-bondline could be ignored for the chamfering joint with low elastic modulus of adhesive.

Compressive Experiment and Damage Simulation Studies of Composite Structure with Plies Drop-off

SHAO Xiao-jun, YUE Zhu-feng, WANG Yi, ZHANG Qing-mao

2007, 27(5): 95-100.

[Abstract](1454) [PDF 1055KB](253)

Abstract:
Composite structure with plies drop-off is studied by compressive experiment and FEM.A user subroutine is implemented to ABAQUS to simulate the damage of structure.The simulation results agree well with experimental data.The experimental data and FEM simulation results show that the composite structure with plies drop-off is very complex.Especially in the transition segment,the properties of every section are different.At damage simulation,the initiation and development of three types of damage are predicted.The matrix cracking damage and the shearing damage of fiber-matrix occur simultaneously at first,and then fiber buckling damage is founded.The effect of matrix cracking and fiber-matrix shearing is remarkable and catastrophic to the whole structure.Fiber buckling intensifies this effect,the initiation and development of fiber buckling indicates that the structure loses carrying capacity at all.

2007 Vol. 27, No. 5